Lighting unit



March 1, 1938.

c. B. HALVORSON LIGHTING UNIT Filed April 18, 1956 v 2 Sheets-Sheet 1Inventor; Cromwell A. B. Halvor'son,

S yl i Attorney.

March 1, 1938. c. A. B. HALVORSON ,0

LIGHTING UNIT Filed April 1a, 1936 2 Sheets-Sheet 2 Fig.6.

Inventor Cromwell A. B. Halvorson,

Attorney.

Patented Mar. 1, 1938 UNITED STATES LIGHTING UNIT Cromwell A. B.Halvorson, Lynn, Masa, assignor to General Electric Company, acorporation of New York Application April 18,

7 Claims.

My invention relates to lighting units and more particularly to largeluminaires such as are used for lighting sections of highways, orsimilar large areas.

One object of my invention is to provide an improved luminaire whichwill be substantially self-cleansing.

Another object of my invention is to provide an improved deflectorhaving a beam cut-off of less than which will provide an improved lightdistribution.

Another object of my invention is to provide a luminaire which will besubstantially nonglaring to motor vehicle operators.

Another object of my invention is to provide improved means incombination with a reflector for modifying the distribution of lighthorizontally without substantially modifying the distribution invertical planes.

For a better understanding of my invention, together with other andfurther objects thereof, reference is had to the following description,taken in connection with the accompanying drawings and its scope will bepointed out in the appended claims.

In the accompanying drawings, Fig. 1 is a vere tical sectional view of aluminaire built in accordance with my invention; Fig. 2 is a modifiedunit equipped with an improved deflector in accordance with myinvention; Fig. 3 is a perspective view of the deflector used in Fig. 2;Fig. 4 is a plan view of the deflector of Fig. 3 illustrating thedistribution of light thereby in a horizontal plane; Fig. 5 is amodified deflector; Fig. 6 illustrates diagrammatically lightdistribution of the unit shown in Figs. 2, 3 and 4; and Fig. '7 is afragmentary view of a modification of Fig. 1.

Referring to Fig. l in detail, the unit illustrated comprises aninsulator l0 which is supported by a metal collar II. A socket l2containing a lamp I3 is mounted in the insulator ill and a cable [4threaded through a conduit l5 carries current to the socket and lamp.

The lamp I3 is enclosed by a circular reflector I6 and a globe I! whichare sealed to each other at their perlmeters by a flange ill on thereflector l6 which is rolled into grooves in the perimeter of the globeIT. The reflector I6 is further equipped with a sleeve i9, which is ofsuch a diameter that it fits into the open end of the insulator Ill.This sleeve is joined to the reflector, a shoulder 20 being formed, atthis point, which fits up against the lower end of the insulator. Thewhole assembly is attached to the insulator I0 by several spaced latches2| which engage 1936, Serial No. 75,160

hooks 22 on the supporting collar II. The joints between the reflectorand globe and the joint between the insulator and reflector aredustproof. Since there is no other place for air to enter the globe, itremains clean indefinitely. 6 The air space between the cable and cableconduit wall is very small and permits merely enough air to flow in andout of the unit to take care of expansion and contraction resulting fromtemperature changes.

The outside of the reflector I6 is smooth, the reflector being made of ametal sheet such as aluminum, the reflecting surface of which isspecially treated to retain its reflectivity. Any rain striking the unitfreely flows over the surface of the reflector and down over the surfaceof the globe. The flange l8 extends beyond the surface of the reflectoronly enough to extend over the grooved perimeter of the globe. Thegrooved perimeter is slightly thicker than the globe wall, therebyforming a flange, so that the presence of the flange i8 constitutes aslight hindrance to the flow of water from the surface of the reflectorto the surface of the globe.

The proper distribution of light in luminaires of this type becomes ofprimary importance in view of the high intensity source used and of thecomparatively large area over which this available light is to bedistributed. In view of the high intensity of the light source, it isdesirable to conflne the light from the unit within a beam having aspread of less than 180 to avoid glare and to distribute the lightwithin this beam so as to produce a uniform surface brightness upon thehighway surface which is illuminated by the unit.

In order to obtain this desired distribution of light, the center 23 ofthe light source in the lamp I3 is placed on the axis of the reflectorand relatively to the edge of the reflector flange l8 so that a line 24drawn from the edge of the reflector through the center may be at anangle of approximately 10 with a horizontal line through the center.This provides a collecting angle of substantially 200 for the reflector.Although this 200 angle includes the flange l8, it is correct toconsider the flange as a part of the reflector, since its inner surfaceis a continuation of the reflector surface and the glass which is infront of it reduces its reflecting efli- 50 ciency only nominally. Thebeam spread of this reflector is made as nearly supplementary to thecollecting angle as possible since it is found that, for general use,this beam spread is acceptable. These angles represent only the vir- 5tual cut-off angles. some light is projected beyond these cut-off anglesbecause the source has a vertical dimension. The maximum intensity issomewhat below this cut-oil since with this type of reflector it has notbeen practical to provide the maximum intensity immediately below thevirtual cut-off.

The light within this defined beam should be distributed so as toproject a large portion of the generated light flux toward the outerportions of the beam to correspondingly increase the intensity of thelight at the remote portions of the illuminated area. In order toaccomplish this distribution, the reflector is shaped as a complexsurfaced conoid, the surface of which is generated by a curve having anelliptical section and a parabolic section revolved about a verticalaxis. The respective sections of this curve have a common focus in thecenter of the light source, and their respective axes are so arrangedthat the surfaces project light as close to the opposite edge of thereflector as possible. Referring to Fig. l, I have indicated the line 24which represents the virtual cut-off of the beam. The highest can-- diepower or intensity is obtained, however, by projecting a beam ofparallel rays, as indicated by the line 25 intercepting the reflector ata point 26 and passing below the opposite edge of the reflector. Theother edge of the beam is indicated by a line 21 which is parallel toline 25, and is projected from the edge 28 of the reflector. This beamis approximately 15 to the horizontal, and therefore approximately flvedegrees below the virtual cut-off. This section of the reflector,between the edge 28 and the parallel designated by the point 26 istherefore a parabolic curve having its axis passing through the lightcenter 23 and tilted at 15 degrees to the horizontal.

Considering the upper edge 29 of the reflecting surface we find a ray 30from the light source 23 reflected along the line 3| and just clearingthe lower edge 28 of the reflector opposite to the reflecting element.Another ray 32 from the source 23 intercepts the reflector surface atpoint 33 and is reflected along line 34, which is at an angle to the ray3| and intersects it at a point 35 outside of the reflector and belowthe edge of flange l8. The surface between points 26 and 29 is anellipsoid having its secondary focus at point 35. This point 35 is, ofcourse, representative of the focal point of one increment of thissurface. As this curve moves about the vertical axis of the reflector,this point 35 becomes a focal region having the form of a circle. Thereflector, therefore, distributes the light in a parallel beam and in aspread beam, both beams being as far out toward the edge of thereflector and the illuminated area as possible. The reflected light istherefore at the edge of the beam, thereby building up the intensity ofthe light at the edges of the illuminated area. The area closer to theunit is illuminated by direct light from the source, it being mostintense in this area. As a result of this distribution, a substantiallyuniformly bright pattern of light is obtained on the road surface.

When the luminaires, as above described, are mounted on city streetsnear the curbing, the symmetrical light distribution about the axis ofthe luminaire becomes a source of annoyance to adjacent residents andsome means must be employed to throw the light flux toward the street.For this purpose, I provide several im- -cap by a bracket 38.

proved means, one of which is an improved deflector which, incombination with the above described reflector, provides a desired lightdistribution. Figs. 2, 3, and 4 illustrate one example of suchdeflector.

Fig. 2 illustrates a modification of the unit shown in Fig. 1. In thismodification the reflector l6 and globe I! are the same as in Fig. 1,but instead of the insulator ID a metal cap 36 is used. The socket 31 isattached to this The reflector I6 is attached to the cap 36 by latches2| and is further connected to the cap by a chain 38 attached at one endto the flange I9 of the reflector and of the other end to the cap 36through a rod 40 and screw 4|.

The deflector comprises a pair of reflectors and 46 arranged in suchrelation to the lamp I3 and its light source that it intercepts asubstantial portion of the light flux normally directed towards theadjacent houses and projects this in directions along the street orhighway on each side of the luminaire. This is well indicated in Figs. 3and 4. Reflector 45 is therein disclosed as being nearest to the lightsource.

It is outwardly shaped to flt into the globe its upper edge extending upto the intersection of the globe I1 and the flange I6. This reflector isplaced close to the light source and is,

therefore, cut out to accommodate the lamp bulb l3. Ears 41 and 48 areprovided to intercept light which would otherwise project back of theluminaire. The reflector surface on either side of the light source isshaped to conform to a parabola having its focus, or focal linecoinciding with the axis of the reflector which passes through thecenter 23 and its axis horizontally moved 15 towards the street. Lightrays 49, therefore, striking this surface are deflected towards thestreet, as indicated by the line 50.

The reflector 46 comprises a pair of parabolic cylinder surfaces 5| and62, the focus, or focal line, of which also coincides with the reflectoraxis through the center 23 of the light source.

These surfaces deflect the light projected through the cut-out portionof deflector 45. The reflector 46 is also formed to flt into the globeII. It is attached to the deflector 45 by a set of brackets 53, 54, and55, bracket 54 holding the lower ends of the deflectors and brackets 53and 55 spacing the upper corners thereof. The brackets 53 and 55 are inturn attached to the main reflector l6 by brackets 56 and 51,respectively.

In Fig. 5, I have illustrated a modification of my deflector. Thedeflector herein shown comprises substantially two deflectors, such asshown in Figs. 2, 3, and 4, mounted on opposite sides of the lamp andreflector axis. Thus, we have members 60 and 6| corresponding to member45 on opposite sides of the lamp axis and members 62 and 63corresponding to deflector 46 mounted directly in back of the members 66and 6|, respectively. The lower edge of these reflectors are spaced by astrap 64 which is made of the same materialas the reflectors and isshaped to conform to the usual globe that is ordinarily used with theseunits. This modification may readily be used without the globe I'I,shown in Figs. 1. 2, and 4.

In Fig. 6, I have illustrated the light distribution obtainable with thelighting unit as'illustrated in Figs. 2, 3, and 4. The curve 65 is theaverage of the readings obtained in a series of vertical planes. Thecurve 66 indicates the readings obtained in a cone of from the verticalaxis of the light source. The curve 65 clearly indicates the maximumcandle power or intensity, being at approximately 15 below thehorizontal and the virtual cut-off being somewhat above this, thislatter point being difficult to determine. The curve 66 clearlyindicates the distribution horizontally away from the house side of theluminaire and toward the street side.

The globe i1 shown in Fig. 1 may be of clear glass or may be of rippledglass as indicated at 10, this rippling comprising a series ofirregularly spaced cylindrical protuberances tending to disperse lightat right angles to their respective axes. In addition to these rippleson the outside of the globe, it may be desirable to provide groups ofprisms on the inside of the globe. Fig. 7 illustrates a fragment of saidglobe having prisms on the inner surface, as indicated at 1|, fordeflecting the light away from the house side of the unit and projectingit in the manner shown in the distribution curves for the deflectors.These prisms are substantially vertical and effect a redistribution oflight in the horizontal planes but do not change substantially thedistribution in vertical planes the light projected by the reflector l6.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In a street-lighting unit, the combination of a light source, areflector having a collecting angle greater than 180 comprising aparaboloidal surface and an ellipsoidal surface, the said parabololdalsurface extending from the edge of said reflector toward the axisthereof and arranged to project a parallel beam, the upper edge of whichclears the opposite edge of the reflector,

and said ellipsoidal surface, the secondary focal region thereof beingoutside of said reflector whereby substantially all of the reflectedlight is projected below the edge of the reflector and away from thevicinity of the unit, and the direct light only illuminates the regionimmediately below said unit.

2. In a street-lighting unit, the combination of a conoidal reflectorhaving a vertical axis and a collecting angle of at least and a set ofdeflectors attached to said reflector and extending below the edgethereof comprising parabolic cylinders arranged parallel to the axis ofsaid reflector and arranged to deflect that segment of the normallysymmetrical beam which is projected toward said deflector intopredetermined directions horizontally, so as to add the light of thissegment to the remaining segment of the beam without altering the beamspread.

3. In a street-lighting unit, the combination of a light source, aconoidal reflector having a vertical axis and a collecting angle of notless than 180 arranged to collect the light projected upwardly from saidsource and redirect it in a. beam having a predetermined spreadsymmetrically about its axis, a bowl-shaped globe attached to the openend of said reflector and a deflector attached to said reflector andprojecting into said bowl comprising a curved surface having its focalaxis coinciding with the axis of said reflector and arranged toredistribute the light from said flux in horizontal planes withoutmaterially affecting the vertical distribution of said light flux.

4. In a street-lighting unit, the combination of a conoidal reflectorhaving a vertical axis and a collecting angle of not less than 180arranged to collect upwardly projected light from a source at its focusand to redirect it symmetrically about said vertical axis, a globeattached to the open end of said reflector, a deflector within saidglobe comprising a plurality of curved reflecting surfaces arrangedparallel to each other and to the axis of said reflector for changingthe horizontal distribution about said vertical axis.

5. In a street-lighting unit, the combination of a conoidal reflectorhaving a vertical axis and a collecting angle of not less than 180arranged to collect upwardly projected light from a source located atits focus and to redirect it symmetrically about a vertical axis, aglobe attached to the open end of said reflector, a deflector withinsaid globe comprising a plurality of parabolic cylinders having theirrespective axes coincident with the axis of said reflector and parallelto each other on opposite sides of said reflector axis for changing thehorizontal distribution of the light projected by said reflector intotwo definite directions.

6. In a street lighting luminaire, the combination of a light source anda reflector, said reflector comprising a surface of revolution generatedby a curve comprising a parabolic section extending between the loweredge of said surface to a point intersected by a line drawn parallel tothe axis of said parabolic curve and Passing below the opposite edge ofsaid surface, and an elliptical section adjacent to said parabolicsection, said elliptic section having a focus in the center of saidlight source, and a conjugate focal region immediately below the loweredge of said surface, whereby the light flux projected from saidelliptical surface of revolution is. projected to the focal regionimmediately below the edge of said surface of revolution, and thereafterspread into a beam, whereby substantially all of the reflected lightfrom said surface of revolution is projected away from the regionimmediately below said luminaire.

7. In a street lighting unit the combination of a light source, aconoidal reflector having a collecting angle greater than 180 comprisinga. parabololdal surface and an ellipsoidal surface, said parabololdalsurface extending from the open end of said reflector toward the axisthereof and arranged to project a parallel beam, the upper edge of whichclears the opposite edge of the reflector, said ellipsoidal surfaceextending beyond said parabololdal surface and towards the axis of saidreflector and having a secondary focal region outside of said reflector,said region being sufliciently beyond the edge of said reflector so thatsubstantially no light projected by said elliptical surface isintercepted by the opposite edge of said reflector, wherebysubstantially all of said light is projected away from the regiondirectly below said reflector, said region being illuminated only bydirect light from said light source.

CROMWELL A. B. HALVORSON.

